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 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.lang;

/**
 * The {@code Byte} class wraps a value of primitive type {@code byte}
 * in an object.  An object of type {@code Byte} contains a single
 * field whose type is {@code byte}.
 *
 * <p>In addition, this class provides several methods for converting
 * a {@code byte} to a {@code String} and a {@code String} to a {@code
 * byte}, as well as other constants and methods useful when dealing
 * with a {@code byte}.
 *
 * @author Nakul Saraiya
 * @author Joseph D. Darcy
 * @see java.lang.Number
 * @since JDK1.1
 */
public final class Byte extends Number implements Comparable<Byte> {

  /**
   * A constant holding the minimum value a {@code byte} can
   * have, -2<sup>7</sup>.
   */
  public static final byte MIN_VALUE = -128;

  /**
   * A constant holding the maximum value a {@code byte} can
   * have, 2<sup>7</sup>-1.
   */
  public static final byte MAX_VALUE = 127;

  /**
   * The {@code Class} instance representing the primitive type
   * {@code byte}.
   */
  @SuppressWarnings("unchecked")
  public static final Class<Byte> TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");

  /**
   * Returns a new {@code String} object representing the
   * specified {@code byte}. The radix is assumed to be 10.
   *
   * @param b the {@code byte} to be converted
   * @return the string representation of the specified {@code byte}
   * @see java.lang.Integer#toString(int)
   */
  public static String toString(byte b) {
    return Integer.toString((int) b, 10);
  }

  private static class ByteCache {

    private ByteCache() {
    }

    static final Byte cache[] = new Byte[-(-128) + 127 + 1];

    static {
      for (int i = 0; i < cache.length; i++) {
        cache[i] = new Byte((byte) (i - 128));
      }
    }
  }

  /**
   * Returns a {@code Byte} instance representing the specified
   * {@code byte} value.
   * If a new {@code Byte} instance is not required, this method
   * should generally be used in preference to the constructor
   * {@link #Byte(byte)}, as this method is likely to yield
   * significantly better space and time performance since
   * all byte values are cached.
   *
   * @param b a byte value.
   * @return a {@code Byte} instance representing {@code b}.
   * @since 1.5
   */
  public static Byte valueOf(byte b) {
    final int offset = 128;
    return ByteCache.cache[(int) b + offset];
  }

  /**
   * Parses the string argument as a signed {@code byte} in the
   * radix specified by the second argument. The characters in the
   * string must all be digits, of the specified radix (as
   * determined by whether {@link java.lang.Character#digit(char,
   * int)} returns a nonnegative value) except that the first
   * character may be an ASCII minus sign {@code '-'}
   * ({@code '\u005Cu002D'}) to indicate a negative value or an
   * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
   * indicate a positive value.  The resulting {@code byte} value is
   * returned.
   *
   * <p>An exception of type {@code NumberFormatException} is
   * thrown if any of the following situations occurs:
   * <ul>
   * <li> The first argument is {@code null} or is a string of
   * length zero.
   *
   * <li> The radix is either smaller than {@link
   * java.lang.Character#MIN_RADIX} or larger than {@link
   * java.lang.Character#MAX_RADIX}.
   *
   * <li> Any character of the string is not a digit of the
   * specified radix, except that the first character may be a minus
   * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
   * {@code '+'} ({@code '\u005Cu002B'}) provided that the
   * string is longer than length 1.
   *
   * <li> The value represented by the string is not a value of type
   * {@code byte}.
   * </ul>
   *
   * @param s the {@code String} containing the {@code byte} representation to be parsed
   * @param radix the radix to be used while parsing {@code s}
   * @return the {@code byte} value represented by the string argument in the specified radix
   * @throws NumberFormatException If the string does not contain a parsable {@code byte}.
   */
  public static byte parseByte(String s, int radix)
      throws NumberFormatException {
    int i = Integer.parseInt(s, radix);
    if (i < MIN_VALUE || i > MAX_VALUE) {
      throw new NumberFormatException(
          "Value out of range. Value:\"" + s + "\" Radix:" + radix);
    }
    return (byte) i;
  }

  /**
   * Parses the string argument as a signed decimal {@code
   * byte}. The characters in the string must all be decimal digits,
   * except that the first character may be an ASCII minus sign
   * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
   * value or an ASCII plus sign {@code '+'}
   * ({@code '\u005Cu002B'}) to indicate a positive value. The
   * resulting {@code byte} value is returned, exactly as if the
   * argument and the radix 10 were given as arguments to the {@link
   * #parseByte(java.lang.String, int)} method.
   *
   * @param s a {@code String} containing the {@code byte} representation to be parsed
   * @return the {@code byte} value represented by the argument in decimal
   * @throws NumberFormatException if the string does not contain a parsable {@code byte}.
   */
  public static byte parseByte(String s) throws NumberFormatException {
    return parseByte(s, 10);
  }

  /**
   * Returns a {@code Byte} object holding the value
   * extracted from the specified {@code String} when parsed
   * with the radix given by the second argument. The first argument
   * is interpreted as representing a signed {@code byte} in
   * the radix specified by the second argument, exactly as if the
   * argument were given to the {@link #parseByte(java.lang.String,
   * int)} method. The result is a {@code Byte} object that
   * represents the {@code byte} value specified by the string.
   *
   * <p> In other words, this method returns a {@code Byte} object
   * equal to the value of:
   *
   * <blockquote>
   * {@code new Byte(Byte.parseByte(s, radix))}
   * </blockquote>
   *
   * @param s the string to be parsed
   * @param radix the radix to be used in interpreting {@code s}
   * @return a {@code Byte} object holding the value represented by the string argument in the
   * specified radix.
   * @throws NumberFormatException If the {@code String} does not contain a parsable {@code byte}.
   */
  public static Byte valueOf(String s, int radix)
      throws NumberFormatException {
    return valueOf(parseByte(s, radix));
  }

  /**
   * Returns a {@code Byte} object holding the value
   * given by the specified {@code String}. The argument is
   * interpreted as representing a signed decimal {@code byte},
   * exactly as if the argument were given to the {@link
   * #parseByte(java.lang.String)} method. The result is a
   * {@code Byte} object that represents the {@code byte}
   * value specified by the string.
   *
   * <p> In other words, this method returns a {@code Byte} object
   * equal to the value of:
   *
   * <blockquote>
   * {@code new Byte(Byte.parseByte(s))}
   * </blockquote>
   *
   * @param s the string to be parsed
   * @return a {@code Byte} object holding the value represented by the string argument
   * @throws NumberFormatException If the {@code String} does not contain a parsable {@code byte}.
   */
  public static Byte valueOf(String s) throws NumberFormatException {
    return valueOf(s, 10);
  }

  /**
   * Decodes a {@code String} into a {@code Byte}.
   * Accepts decimal, hexadecimal, and octal numbers given by
   * the following grammar:
   *
   * <blockquote>
   * <dl>
   * <dt><i>DecodableString:</i>
   * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
   * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
   * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
   * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
   * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
   *
   * <dt><i>Sign:</i>
   * <dd>{@code -}
   * <dd>{@code +}
   * </dl>
   * </blockquote>
   *
   * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
   * are as defined in section 3.10.1 of
   * <cite>The Java&trade; Language Specification</cite>,
   * except that underscores are not accepted between digits.
   *
   * <p>The sequence of characters following an optional
   * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
   * "{@code #}", or leading zero) is parsed as by the {@code
   * Byte.parseByte} method with the indicated radix (10, 16, or 8).
   * This sequence of characters must represent a positive value or
   * a {@link NumberFormatException} will be thrown.  The result is
   * negated if first character of the specified {@code String} is
   * the minus sign.  No whitespace characters are permitted in the
   * {@code String}.
   *
   * @param nm the {@code String} to decode.
   * @return a {@code Byte} object holding the {@code byte} value represented by {@code nm}
   * @throws NumberFormatException if the {@code String} does not contain a parsable {@code byte}.
   * @see java.lang.Byte#parseByte(java.lang.String, int)
   */
  public static Byte decode(String nm) throws NumberFormatException {
    int i = Integer.decode(nm);
    if (i < MIN_VALUE || i > MAX_VALUE) {
      throw new NumberFormatException(
          "Value " + i + " out of range from input " + nm);
    }
    return valueOf((byte) i);
  }

  /**
   * The value of the {@code Byte}.
   *
   * @serial
   */
  private final byte value;

  /**
   * Constructs a newly allocated {@code Byte} object that
   * represents the specified {@code byte} value.
   *
   * @param value the value to be represented by the {@code Byte}.
   */
  public Byte(byte value) {
    this.value = value;
  }

  /**
   * Constructs a newly allocated {@code Byte} object that
   * represents the {@code byte} value indicated by the
   * {@code String} parameter. The string is converted to a
   * {@code byte} value in exactly the manner used by the
   * {@code parseByte} method for radix 10.
   *
   * @param s the {@code String} to be converted to a {@code Byte}
   * @throws NumberFormatException If the {@code String} does not contain a parsable {@code byte}.
   * @see java.lang.Byte#parseByte(java.lang.String, int)
   */
  public Byte(String s) throws NumberFormatException {
    this.value = parseByte(s, 10);
  }

  /**
   * Returns the value of this {@code Byte} as a
   * {@code byte}.
   */
  public byte byteValue() {
    return value;
  }

  /**
   * Returns the value of this {@code Byte} as a {@code short} after
   * a widening primitive conversion.
   *
   * @jls 5.1.2 Widening Primitive Conversions
   */
  public short shortValue() {
    return (short) value;
  }

  /**
   * Returns the value of this {@code Byte} as an {@code int} after
   * a widening primitive conversion.
   *
   * @jls 5.1.2 Widening Primitive Conversions
   */
  public int intValue() {
    return (int) value;
  }

  /**
   * Returns the value of this {@code Byte} as a {@code long} after
   * a widening primitive conversion.
   *
   * @jls 5.1.2 Widening Primitive Conversions
   */
  public long longValue() {
    return (long) value;
  }

  /**
   * Returns the value of this {@code Byte} as a {@code float} after
   * a widening primitive conversion.
   *
   * @jls 5.1.2 Widening Primitive Conversions
   */
  public float floatValue() {
    return (float) value;
  }

  /**
   * Returns the value of this {@code Byte} as a {@code double}
   * after a widening primitive conversion.
   *
   * @jls 5.1.2 Widening Primitive Conversions
   */
  public double doubleValue() {
    return (double) value;
  }

  /**
   * Returns a {@code String} object representing this
   * {@code Byte}'s value.  The value is converted to signed
   * decimal representation and returned as a string, exactly as if
   * the {@code byte} value were given as an argument to the
   * {@link java.lang.Byte#toString(byte)} method.
   *
   * @return a string representation of the value of this object in base&nbsp;10.
   */
  public String toString() {
    return Integer.toString((int) value);
  }

  /**
   * Returns a hash code for this {@code Byte}; equal to the result
   * of invoking {@code intValue()}.
   *
   * @return a hash code value for this {@code Byte}
   */
  @Override
  public int hashCode() {
    return Byte.hashCode(value);
  }

  /**
   * Returns a hash code for a {@code byte} value; compatible with
   * {@code Byte.hashCode()}.
   *
   * @param value the value to hash
   * @return a hash code value for a {@code byte} value.
   * @since 1.8
   */
  public static int hashCode(byte value) {
    return (int) value;
  }

  /**
   * Compares this object to the specified object.  The result is
   * {@code true} if and only if the argument is not
   * {@code null} and is a {@code Byte} object that
   * contains the same {@code byte} value as this object.
   *
   * @param obj the object to compare with
   * @return {@code true} if the objects are the same; {@code false} otherwise.
   */
  public boolean equals(Object obj) {
    if (obj instanceof Byte) {
      return value == ((Byte) obj).byteValue();
    }
    return false;
  }

  /**
   * Compares two {@code Byte} objects numerically.
   *
   * @param anotherByte the {@code Byte} to be compared.
   * @return the value {@code 0} if this {@code Byte} is equal to the argument {@code Byte}; a value
   * less than {@code 0} if this {@code Byte} is numerically less than the argument {@code Byte};
   * and a value greater than {@code 0} if this {@code Byte} is numerically greater than the
   * argument {@code Byte} (signed comparison).
   * @since 1.2
   */
  public int compareTo(Byte anotherByte) {
    return compare(this.value, anotherByte.value);
  }

  /**
   * Compares two {@code byte} values numerically.
   * The value returned is identical to what would be returned by:
   * <pre>
   *    Byte.valueOf(x).compareTo(Byte.valueOf(y))
   * </pre>
   *
   * @param x the first {@code byte} to compare
   * @param y the second {@code byte} to compare
   * @return the value {@code 0} if {@code x == y}; a value less than {@code 0} if {@code x < y};
   * and a value greater than {@code 0} if {@code x > y}
   * @since 1.7
   */
  public static int compare(byte x, byte y) {
    return x - y;
  }

  /**
   * Converts the argument to an {@code int} by an unsigned
   * conversion.  In an unsigned conversion to an {@code int}, the
   * high-order 24 bits of the {@code int} are zero and the
   * low-order 8 bits are equal to the bits of the {@code byte} argument.
   *
   * Consequently, zero and positive {@code byte} values are mapped
   * to a numerically equal {@code int} value and negative {@code
   * byte} values are mapped to an {@code int} value equal to the
   * input plus 2<sup>8</sup>.
   *
   * @param x the value to convert to an unsigned {@code int}
   * @return the argument converted to {@code int} by an unsigned conversion
   * @since 1.8
   */
  public static int toUnsignedInt(byte x) {
    return ((int) x) & 0xff;
  }

  /**
   * Converts the argument to a {@code long} by an unsigned
   * conversion.  In an unsigned conversion to a {@code long}, the
   * high-order 56 bits of the {@code long} are zero and the
   * low-order 8 bits are equal to the bits of the {@code byte} argument.
   *
   * Consequently, zero and positive {@code byte} values are mapped
   * to a numerically equal {@code long} value and negative {@code
   * byte} values are mapped to a {@code long} value equal to the
   * input plus 2<sup>8</sup>.
   *
   * @param x the value to convert to an unsigned {@code long}
   * @return the argument converted to {@code long} by an unsigned conversion
   * @since 1.8
   */
  public static long toUnsignedLong(byte x) {
    return ((long) x) & 0xffL;
  }


  /**
   * The number of bits used to represent a {@code byte} value in two's
   * complement binary form.
   *
   * @since 1.5
   */
  public static final int SIZE = 8;

  /**
   * The number of bytes used to represent a {@code byte} value in two's
   * complement binary form.
   *
   * @since 1.8
   */
  public static final int BYTES = SIZE / Byte.SIZE;

  /**
   * use serialVersionUID from JDK 1.1. for interoperability
   */
  private static final long serialVersionUID = -7183698231559129828L;
}
